Synchronous code telegraphy.



No. 726,736. PATENIED APR. 28, 1903.

E. F. ,NORTHRUP. v SYNGHRONOUS CODE TBLEGRAPHY.

APPLICATION FILED JAN. 2, 1903. V N0 MODEL. lrnnnrs-snnm 1..

Q l i m: Nomsyflws cu. PHOYO-LITHLL, WASHINGTON. D. c.

' E. F. NORTHRUP.

SYNGHRONOUS GODE TELEGRAPHY.

APPLICATION FILED JAN. 2,1903.

N0 MODEL. v 2 SHEETS-SHEET 2.

-TLGEJ- PATENT @FFICE.

EDWIN F. NORTHRUP, on PHILADELPHIA, PENNSYLVANIA.

SYNCHRONOUS CODE TELEG RAPHY.

SPECIFICATION forming part of Letters,

Patent No. 726,736, dated April 28, 1903.

Original application filed October 10,1902. Serial No. 126,744. Divided and this application filed January 2, 1903. Serial (No model.)

To aZZ whom it may concern:

Be it known that I, EDWIN F. NORTHRUP, a citizen of the United States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Synchro nous Code Telegraphy, of which the following is a specification.

My invention relates to improvements in wire telegraphy, and more especially to a synchronous multiplex code telegraph system employing an alternating current for trans mission.

The principal object of Iny invention is the adaptation of the alternating current for the transmission of Morse characters in the simplest possible manner and the providing of means whereby the very troublesome system of quadruplex Morse telegraphy now in general use may be supplanted by a system in which the line-relays when once; balanced need no adjustment for weather and other changes, which so readily affect the Edison quadruplex.

According to my invention the line is multiplexed by the well-known method "of em ploying synchronously-operated sunflowers, which allow the local operators the use of the line successively at rapidly-recurring intervals, and the line is also duplexed by balancing, so that at least four operators can be transmitting at eachend of the lineat the same timethat is to say, the capacity of the line is at leasteight simultaneous messages...

Myinvention,moreover,makesit possible to employthe well-known Morse keys and sounders or registers or other well-known code-telegraph receivers without the necessity of devising special transmitters andreceivers. The signals are impressed on the line by reversing inipulses'of the line-current-for example, by reversing one impulse for a dot and two for a long dash or any multiple of these numbers. In this manner I'make up a complete Morse code which is readily receivable upon any of the well-known receiving instruments above referred to.

In order to more fully describe my invention, reference will be had to the accompanying drawings, in which- Figure l is a diagram illustratingtheprinciple of my invention and the simple casein whichthe line is used by a single operator transmitting messages to a single receiver. Fig. 2 represents a modified form of Morse key designed to reduce sparkin Fig. 3 is a diagram illustrating my method of forming a Morse code with alternating-current impulses. Fig. 4 is a diagram representing a transmitting and receiving apparatus at one end of an octoplex line, and Fig. 5 is a diagram illustrating the principle of dnplexing the system.

r Similar characters refer to similar parts throughout the several views.

I willtirst describe the manner in which a single operator transmits signals, then how these are received, and finally how the line may beworked duplex or octopleXI The transmitting of the dots and dashes of the Morse alphabet is accompanied by reversing oneimpulse or semicycle of the alternating current for a dot, two impulses for a short dash, and four impulses fora long dash,

or preferably a multiple of these numbers. The apparatus herein shown, however, is so arranged that a single operator can reverse only every fourth impulse. Hence the time occupied in sending a long dash is equal to sixteen impulses of the line-current. The term-impulses is herein used as synonymous with semicycle and half-period, being that portion of the current included between two successive zero-points.

Referring to Fig. 1, a represents a commutator used as a current-reverserand driven by any suitable motive power. The direct current enters this commutator by the leads a a and the alternating current leaves it by the leads a a. The alternating current developed by this commutator completes its circuit through the primary of. a small transformer b. This transformer has two secondary windings b and 19 with their turns wound in opposite directions. The secondary wind ings are connected to earth,as by conductor b as shown. The commutator a, simply represents a source of alternating current and may be an alternating-current dynamo or any device for producing an alternating electric current. Moreover, I do not confine Inyinvention to any special form of current-wave. A

ice

Morse key 0 is pivoted, as at c,and is provided with the contacts 0 0 Operating in conjunction with this key is a sunflower cl, provided with along segment d which extends around three-fourths of the circumference of the su nflower, and a short segment d, which extends over the remaining one-fourth of the circumference, the segment d being connected to the point 0' of the key, while the segment d is connected to the lower key-contact 0 This sunflower is provided with a trailer 6, which revolves around the sunflower and over the segments at such a speed that the said trailer makes one complete revolution around the sunflower for each four complete impulses developed by the comm ntator ct. This trailer is driven preferably at a constant speed and may be mechanically geared to the shaft which drives the commutator (I, or may be driven in any suitable manner. This sunflower may be provided with four segments of equal circumferential length and three connected to the wire which segment d now connects to, while the fourth would be the segment cl. This, however, would be neces sary only in case four operators wished to use the sunflower, which case will be hereinafter described. Since this trailer makes one complete revolution for each four impulses, it will therefore pass over the seg ment (1' for each fourth impulse developed and over the long segment d for the other three. When the key is not depressed, the alternating current induced in the winding 1') of the transformer will flow down the main line, going only one-fourth the time by way of the key and into segment (1 of the sunflower and for the rest of the time through the segment (1. Every fourth impulse can therefore be controlled or modified by the key, and there will be a current on the line at all times. If the key is depressed when the trailer is on segment d the secondary winding b of the transformer is connected to the key through the contact c and as soon as the trailer 6 reaches segment (1 the line will receive current from this winding of the transformer. The current, however, from the winding Z1 is in opposite direction to the current which comes from the winding 1), and hence depressing the key reverses every fourth impulse of the current. If the key is kept depressed only long enough to reverse one impulse,a dot will be transmitted, iflong enough to reverse two impulses a short dash, and if long enough to reverse four impulses a long dash. This order of modifying the impulses will hold for any multiples of these numbers.

In Fig. 3 I have shown how the line-current is modified to send the letter A, represented by a dot, space, and dash. In this case two impulses are reversed for a dot or short dash, which is the same thing, and four for a long dash. The same rule may be applied to forming all the characters of the Morse code. If by chance an operator should depress the key at the instant the trailer eis passing over the segment (1, the reversal of the current would be attempted when the impulse was at a maximum, and this would probably cause a spark at 0 I have, however, devised a modified form of Morse key, (shown in Fig. 2,) which will reduce this sparking to a minimum. In this case I provide the key with a thin steel spring extension 0, which is adapted to move between the poles of an electromagnet 0 when the key is depressed. This magnet has two windings c and 0 one connected in series with keycontact 0 and transformer secondary b and the other in series with the key-contact c and transformer secondary b. If the spring is against contact 0 and current is flowing through coil 0', then even if the key is depressed the contact will not be broken at 0 since the spring will be attracted down by the magnet and will only bend; but if the key is kept depressed and the current through the coil 0 ceases then the spring will move up and contact will be made at 0 If current then flows through coil the contact at 0 will remain closed even if the key is raised. Thus no sparking of any consequence can ever occur at contacts 0 and 0 In any case, however, the sparking will be small, and hence I do not consider this modified form of key essential for the successful operation of the system.

Referring now to the receiving end of the line, Fig. 1, the current transmitted overthe line, as above described, maintains in vibration the tongue of a polarized relay f and then passes to earth, as shown. The local receiving apparatus consists of two sunflowers (Z and d similar to sunflower d, a local relayf with two independent coils f and f a sounder g or Morse register, Bain chemical receiver or other well known receiver of Morse or similar characters, and a source of local current h, all connected as shown. The trailers e and e rotate in synchronism with the transmitting-trailer e and, like trailer 6, makes one complete revolution for every four impulses of the line-current arriving. I do mot herein claim any special method or means for maintaining synchronism between these trailers, as this may be done in a variety of ways. A method of maintaining synchronism well adapted to my system has been described in Nature, May 28, 1878, also in Lord Rayleighs Theory of Sound, Vol. I, page 67. Other methods are described in the patents to Henry A. Rowland, Nos. 622,636, 689,753, 691,667, and others. The sunflowers d and d would in practice comprise two sections of one sunflower, but are represented separately in the diagram for the sake of clearness.

The operation of the receiving apparatus is as follows: Let it be assumed that as long as none 'of the impulses are reversed the tongue of the main-line relayf will always be against its right-hand contact when the trailers e and c are passing over the short segments. In this event whenever trailer e arrives on the short segment of its sunflower the right-hand coil f of the relay f will receive current from the battery h, and the tongue of this relay will be drawn against its back-stop. If, however, at the time the trailers arrive on the short segments an impulse is reversed, the tongue of relay f will be against its left-hand contact instead of its rightthat is, against the contact to which it was drawn by the preceding impulse. The local circuit will then be completed through the left-hand coilf of the relayf, which will draw the tongue of said relay against its forward contact, Where it will remain until the trailers again return to the short segment, when the tongue will return to its back-stop unless another impulse has been reversed. If this be so, then the tongue Willremain against its contact for another revolution of the trailers. As long as impulses continue to be reversed, whenever the trailers arrive on the short segments, just so long will the tongue of the relay f remain against its forward contact. The shortest possible time of making a single dot of the Morse alphabet is therefore equal to the time of one revolution of the trailer. In general, however, a dot will correspond to two or more revolutions and the dash correspondinglyincreased. Obviously, then, the closing of this relay-contact for various lengths of time determined by the number of impulses reversed may be made to operate a Morse sounder g or register, chemical-receiver, or any of the receivers of Morse or similar characters. I have shown a sounder g connected in circuit with a battery hand the tongue and forward contact of the relay f; but obviously, if desired, I may use the relay f alone as a sounder or as a visual receiver- Since the operator transmitting may depress his key when his sunflower-trailer is at any part of its revolution, it would appear that if the key were to be depressed when the trailer was leavingthe short segment (1 and raised before the trailer returns again to this segment no impulse would be reversed. This, however, is not the case, since the trailer rotates at so great a speed'that it will make more than one revolution before the hand having depressed the key can allow it to rise again. Moreover, there will be a difference in the duration of a dot or dash at the transmitting end of the line and a dot or dashreceived at the receiving end-that is to say, a dash transmitted will not necessarily be of the same length or duration as a dash received, but this difierence diminishes as the number of impulses that make up a dot or dash are increased. There will be a greater uniformity when four impulses are reversed for a dot and eight for a dash than when two are reversed for a dot and four for a dash. The time representing a dot of four reversed impulses, or eight impulses in all, is, however, very brief, although the mark indicating the dot in Fig. 3 seems rather long. This will be more apparent when we consider that the characters may be sent line always has a greater speed capacity than 7 an operator.

'From the foregoing descriptionit will .be seen that it is not necessary for each operator to reverse or otherwise modify the same number of impulses always for a given element of the code, it being essential only that the number of impulsesmodified for one element shall bear a certain relation to those modified for the other element of a given character. For example, a certain operator may transmit'by modifying two impulses for a dot and four fora dash, while the same or another operator with the same or similar apparatus may transmit by modifying four impulses for a dot and eight for a dash. In other words, the same limitations apply in this system as to the relation between the elements of the code as in the ordinary Morse system. Of course if a given operator commences to transmit amessageand his speed of transmission is such that he holds down his key long enough to reverse two impulses for a dot and four for a dash he must prefer: ably maintain the same rate during the trans.- mission of the message. The reversed impulse will of course not have the exact form at the receiving end of the line as shown in the diagram Fig. 3 of the impulses as they pass from the transmitter, but they will be flattened somewhat, though there will be no harmful results at the receiving end of the line, due to a tailing out or running together .of the impulses.

The principles above explained, whereby a single operator may transmit Morse signals in one direction, may be readily extended to multiplex and duplex transmission. v

The apparatus and one end of an octoplexapparatus at both ends of such a line are identical, with the exception that atone of the stations the commutator for producing line connections are shown in Fig. 4. The

the alternating current and the trailers are simply drivenat a desired steady speed by any suitable motor, Whereas the motor corresponding to this one at the other station has its speed regulated to synchronize with the first-mentioned motor. Inother words, it is necessary to provide a synchronizing device of a dilferentially-wound main-line relayf",

having one of its coils connected to the real lineZ and the other to the artificial linelfl In this way the line is duplexed. Tlhetransmitting and receiving sunflowers d and ax d are in this case provided each with four segments corresponding to the short segment of the sunflowers shown in Fig. 1 and are indi;

cated as segments 1, 2, 3, and 4, respectively. Correspondingly-numbered segments of the receiving-sunflower are connected to the right and left hand coils of the local relays 1 2 F3, and 4 as shown, while the four keys 1, 2 8, and 4 are connected each to its respective segment of the transmitting-sunflower. The key-contacts are connected in multiple across the wires leading from the two secondaries of the transformer I). The commutator a and its connections are the same asshown in Fig. 1. The relays I to 4 may obviously be connected to any suitable receiving instrument, such as a sounder or others described with reference to Fig. 1, or may alone be utilized as receivers or sounders. Inasmuch as the main-line relay isbalanced and responds only to impulses from the other end 'of the line, the operation of the keys does not affect the home relay, and hence the receiving apparatus may be in operation at the same time that the keys are being operated at the station. Moreover, the keys may be operated at Will withoutin the least interfering with each other, as they can only afiect the line-current when each is given the use of the line by its respective segment of the transmitting-sunflower. Takingeach receiving relay and key separately, its operation is exactly the same as described with reference to Fig. 1, each being independent of the other. By referring to Fig. 4 it will be seen that a person operating key 1 can reverse only the impulses 1 5 9 13, &c., that a person operating key 2 can reverse only impulses 2 6 10 14, due, and so for key 3 the impulses 3 7 ll 15, c. Hence each operatorin transmitting is absolutely independent of the other.

The receivin -rela s 1 to 4 also operate independently of each other. Relay 1 receives signals from its corresponding key 1 at the other end of the line and likewise with relays 2 3 and 4. Thus it is seen how by means of the alternating current eight messages in the form of Morse signals can be sent over a long line at the same time. The number of the messages, however, is not at all limited to eight. For lines of moderate length the frequency of the line-current may be doubled, in which case sixteen messages could be simultaneously transmitted as easily as eight. In fact, the system is exceedingly flexible.

In practice any suitable means may be employed for finding the operatorthat is, determining when a given receiver is adapted to receive messages from its corresponding transmitter and not from some of the other transmitters. This may be done by having a predetermined call and adjusting the receiving-sunflowers or their trailers or switches placed in the segment-circuits of the sunflowers until by trial the impulses sent by a given operator are received upon a corresponding relay. Obviously any of these receiving-relays may receive messages from any of the transmitting-keys dependent upon the relative angular position of the transmitting and receiving segments or trailers or the order in which the relays are connected to the respective segments of the receiving sunflowers.

In Fig. 5 I have shown how the line is duplexed, which consists merely in connecting one of the differential coils of each line-relay to an artificial line Z having capacity and self-induction equal to that of the real line and balancing the line-relay at one end of the line, so that it is sensitive to current from the opposite end of the line only. A line thus balanced needs generally no further adjustment for weather and other changes, when duplexing becomes an easy matter. According to present telegraph practice when (inplexing and quadruplexing is carried on by direct currents the lines are continually getting out of balance, and the instruments necessitate constant adjustment to render them at all operative. With alternating currents this trouble may be greatly diminished.

Having thus described my invention, I do not claim in this application the method which the apparatus herein described is designed to carry out, said method being the subjectmatter of an application filed by me October 10, 1902, for improvements in code telegraphy, Serial No. 126,744, of which the present is a division.

What I do claim as my present invention, and desire to secure by Letters Patent of the United States, is

1. In an electric telegraph, a main line, sources of two simultaneous periodic electromotive forces of different phase, means for normally transmitting to line impulses of the current produced by one of said electromotive forces, and transmitting the characters of a code by substituting for the normal impulses on the line, impulses from the source of said second electromotive force.

2. In an electric telegraph, a main line, sources of two simultaneous alternating electromotive forces of opposite polarity, means for normally transmitting to line impulses of the current produced by one of said electromotive forces, and transmitting the characters of a code by substituting for the normal impulses on the line, impulses from the source of said second electromotive force.

3. In an electric telegraph, a main line, a distributing-sunflower, sources of two simultaneous periodic electromotive forces of different phase, one of said sources of electromotive force normally connected to line through said sunflower, and the other normally disconnected from the line, and makeand-break device adapted, when operated, to break the line connection with one of said sources and to connect the other source of electromotive force to line through said sunflower.

4. In an electric telegraph, a main line, a distributing-sunflower, sources of two simultaneous periodic electromotive forces of opposite polarity, one of said electromotive electromotive force to line through said sun- 5. In an electric telegraph, a main line, a 1

source of periodically-varying electromotive force, a transformer having its primary connected to said source and having two secondary windings prod ncin g simultaneous electromotive forces of different phases, make-andbreak devices connecting one of said secondaries normally to line, and connecting the other of said secondaries to line and disconnecting the first, in the transmission of the elements of a code.

6. In an electric telegraph, a main line, a 1 source of periodically-varying electromotive force, a series of norm ally closed contacts connected to said source of electromotive force,

devices'adapted to close each of the said open contacts upon the breaking of its corresponding normally closed contact, and means for connecting said make-and-break device to the main line successively and at periodicallycontacts alternately in unison with the varyrccurring intervals.

7. In an electric telegraph, a main line, a

plurality of keys, means for connecting the keys to the main line successively and at periodically-recurring intervals, a source of periodically-varying electromotive force connected to the normally closed contacts of said keys, and a source of periodically-varying electromotive force of different phase from the first-mentioned electromotive force, connected to the normally open contact of said keys, whereby the closing of the said normally open contact upon the operation of said keys, sends to line an impulse of a different phase from the normal impulse, and means for receiving the characters of a code, formed of the substituted impulses.

8. In an electric telegraph, a main line, a current-distributing sunflower having a pinrality of segment-circuits, make-and-break devices connected in said circuits, each of said devices having a normally closed and a normally open contact, a source of two simultaneous periodic electromotive forces of opposite polarity, one of said electromotive forces passing to line through the normally closed of said contacts and the other of said electromotive forces passing to line by the normally open contacts upon the closing of the same, whereby the characters of a code are impressed on the line by the substitution of impulses of one polarity in prearranged order, and means for receiving the characters thus transmitted.

9. In an electric telegraph, a main line, a

current-distributing sunflower having a plurality of segment-circuits, a key located in each of said circuits and each key provided with a normally closed and a normally open contact, a source of two simultaneous periodic electromotive forces of opposite polarity passing to line through the normally closed contacts of said keys and the other of said electromotive forces passing to line by the normally open contacts upon the operation of the keys, whereby the characters of a code are impressed on the line by the substitution of impulses of one polarity for those of an opposite polarity in prearranged order, and means for receiving the characters transmitted.

10. In an electric telegraph, a source of periodic electromotive force, a transformer connected thereto and having two oppositelywound secondaries, a plurality of normally closed contacts connected to one of the said secondaries, and a plurality of normally open contacts connected to the other of said secondaries, a plurality of make-and-break de-' vices for said contacts and means for connecting the said make-and-break devices to line successively and at periodically-recurring intervals.

11. In an electric telegraph,the combination with a main line carrying a periodicallyvarying'current, of two electrical contacts, and a contact-maker adapted to engage said ing line-current, two receiving-current-dis:

tributing sunflowers connected to said con;

tacts and operating in unison with said contact-maker, and a local receiving instrument connected in circuit with said sunflowers and said moving contact-maker.

12. In an electric telegraph, the combination with a main line carrying a periodicallyvarying electric current, of two contacts and a contact-maker adapted to engage said contacts alternately in unison with the varying line-current, a neutral double-wound local receiving-relay, a local electric circuit including the contact-maker operating in unison with the main-line current and the two windings of the said local relay, and means for completing said circuit through one of the windings ofsaid relay each time the unison contact-maker engages one of its contacts and completing the local circuit through the other of the windings of said relay-when the said contact-maker remains against its said contact longer than a predetermined time.

13. In an electric telegraph, the combination with a main line carrying a periodicallyvarying electric current, of a main-line relay operating in unison with the variation in said current, sunflower current-distributors, one connected to each of the contacts of said main-line relay, a local relay having two independent windings, one connected in circuit with one of said distributors and a contact of said main-line relay, and the other in circuit with the other of said distributers and the IIO other of said main-line-relay contacts, and a source of current connected to both windings of said local relay and to the tongue of said main-line relay, substantially as described.

14. In an electric telegraph, the combination with a source of periodic electromotive force, a main line, and means for impressing the characters thereon, of a main-line relay, receiving sunflower distributors, one connected to one of the tongue-contacts of said relay and the other distributer to the other of said contacts, each of said distributers having a plurality of corresponding segment-circuits, a plurality of local relays each having independentlywound magnets, one set of corresponding windings of said relays connected in the segment-circuits of one of said distributers while the other set are connected in the segment-circuits of the other distributer and a source of local current connected to all of said local relay-windings and to the tongue of said main-line relay.

15. In an electric telegraph, a main line, a distributing-sunflower, sources of two sim ultaneous periodic clectromotive forces of different phase, one of said sources of electromotive force normally connected to said sunflower and operating therethrough to send to line impulses of a given phase and the other electromotive force normally disconnected from the sunflower, and a make-and-break device adapted, when operated, to break the sunflower connection with one of said sources and to connect the other source of electromotive force through said sunflower, whereby one or more impulses of diiferent phase from the normal are sent to line.

16. In an electric telegraph, a main line, a distributingsunflower, sources of two simultaneous periodic electromotive forces of opposite polarity, one of said electromotive forces normally connected to said sunflower and acting therethrough 'to normally send to line impulses of a given phase, and the other electromotive force normally disconnected from said sunflower, and a key adapted, when operated, to break the connection from the source of one of said electromotive forces and to connect the source of the other electromotive force to said sunflower whereby one or more impulses of different phase from the normal are sent to line.

17. In an electric telegraph, a main line, a source of periodically-varying electromotive force, a series of normally closed contacts connected to said source of electromotive force, a second source of periodic electrornotive force of dilferent phase from the first, a series of normally open contacts connected to the second source, a plurality of make-andbreak devices adapted to close each of the said open contacts upon the breaking of its corresponding normally closed contact, and means for operating in conjunction with said make-and-break devices to send to line imraeyrec pulses of different phase upon the closing of the normally open contacts, from those sent toline upon the closing of the norm ally closed contacts.

18. In an electric telegraph, a main line, a plurality of keys, means for connecting the keys in circuit successively and at periodically-recurring intervals, a source of periodically-varying electromotive force connected to the normally closed contacts of said keys, and a source of periodically-varying electromotive force of different phase from the first mentioned electromotive force, connected to the normally open contact of said keys, the closing of the said normally open contact upon the operation of said keys, sending to line an impulse of a different phase from the normal impulse, and means for receiving the characters of a code, formed of the substituted impulses.

19. In an electric telegraph, a main line, a current-distributing sunflower having a plurality of segment-circuits, make-and-break devices connected in said circuits, each of said devices having a normally closed and a normally open contact, a source of two simultaneous periodic electromotive forces of opposite polarity, one of said electromotive forces passing to the sunflower through the norm ally closed of said contacts and the other of said electromotive forces passing to the sunflower through the normally open contacts upon theclosing of the same.

20. In an electric telegraph, a main line, a current-distributing sunflower having a plurality of segment-circuits, a key located in each of said circuits and each key provided with a normally closed and a normally open contact, a source of two simultaneous pe riodic electromotive forces of opposite polarity, one of said electromotive forces normally passing through the sunflower by the normally closed contacts of said keys, and the other of said electromotive forces passing through the sunflower by the normally open contacts upon the operation of the keys.

21. In an electric telegraph, a source of periodic electromotive force, a transformerconnected thereto and having two oppositelywound secondaries, a plurality of normally closed contacts connected to one of the said secondaries, and a plurality of normally open contacts connected to the other of said secondaries, a plurality of make-and-break devices for said contacts and means for connecting the said make-and-break devices in circuit successively and at periodically-recurring intervals.

In testimony whereof I affiX my signature in presence of two witnesses.

EDWIN F. NORTI-IRUP.

W itucsses:

FRANK G. GRIER, W M. T. KENYON.

IIS 

